Such a device emerges, for example, from EP 2 730 447 A1. The device constructed as a drive control system for a commercial vehicle comprises a power transfer unit for driving the front and rear wheels of the commercial vehicle by means of a drive engine, as a well as a switchover device, which makes it possible to switch between an all-wheel-drive mode in which both the front wheels and also the rear wheels of the commercial vehicle are driven and a two-wheel-drive mode in which only its rear wheels are driven. The switchover is performed here independent of the driver according to a wheel slip detected for the rear wheels. The wheel slip is detected based on a current forward motion speed of the commercial vehicle derived from position information of a GPS module, in which this speed is compared with a theoretically expected forward motion speed of the commercial vehicle that is given from the rotational speed of the drive engine, the gear ratio of a vehicle transmission, and the wheel circumference of the rear wheels. If the wheel slip determined in this way is greater than a given threshold value, the drive control system activates the all-wheel-drive mode by closing an electro-hydraulically actuatable coupling.
On the other hand, the drive control system deactivates the all-wheel-drive mode by opening the hydraulically actuatable coupling and reverts to the two-wheel-drive mode as soon as the detected wheel slip is less than or equal to a specified threshold value and the commercial vehicle is simultaneously located on an essentially non-inclined surface. In addition, a deactivation of the all-wheel-drive mode is also provided for the case of elevated forward motion speeds of the commercial vehicle greater than 20 km/h. The scope in which the front wheels are actually engaged in the driving task during the all-wheel-drive mode is, in contrast, not taken into account. The all-wheel-drive mode is therefore also maintained in situations in which, for example, due to reduced wheel vertical forces on the front wheels, there is no longer sufficient ground contact by the associated front tires.
Therefore, the problem of the present disclosure is to disclose a device of the type specified above that is improved with respect to the criteria used for the driver-independent deactivation of an all-wheel-drive mode.